Forgery-preventing film

ABSTRACT

Disclosed is a forgery-preventing film having, on one side of a first layer (A) comprising a thermoplastic resin, a second layer (B) comprising a thermoplastic resin wherein said film satisfying at least one of the following conditions: Condition 1: one side of said first layer (A) is treated to prevent forgery and said second layer (B) is formed on the surface of the treated side of said first layer (A); Condition 2: said second layer (B) comprises at least two thermoplastic resins of different melt viscosities; Condition 3: porosity of said second layer (B) is greater than porosity of said first layer (A); and Condition 4: a polymer net is formed on one side of said first layer (A) and said second layer (B) is formed on the surface having the polymer net.

TECHNICAL FIELD

[0001] The present invention relates to a forgery-preventing film foruse on bank notes, bills, checks, traveler's checks, securities, cardsand the like, which need to prevent forgery and falsification.

BACKGROUND ART

[0002] In modern society, numerous documents and cards with forgery andduplication being prohibited are in circulation, such as bank notes,checks, securities, and cards. The forgery and duplication of theseitems must not only be prohibited by law, but must also be renderedtechnically impossible to maintain social order. However, copying andduplication technologies have made alarming strides in recent years,with the risk of forgery and duplication increasing each year. The crimeof forgery has been increasing of late, and the techniques employed arebecoming ever more sophisticated.

[0003] Accordingly, various techniques of preventing forgery andduplication have been developed.

[0004] For example, there are techniques of visually detecting forgerybased on external appearance. Specifically, there are techniques ofincorporating fluorescent substances in printed matter; a technique ofprinting with magnetic ink to permit visual detection of the change indensity of the ink by magnetic effects (Japanese Unexamined PatentPublication (KOKAI) Heisei No. 5-177919); the technique of printing withink comprising photochromic light-sensitive pigments (JapaneseUnexamined Patent Publication (KOKAI) Showa No. 60-79992); techniques ofprinting with ink having specific reflection spectroscopiccharacteristics or two or more inks having differences in reflectanceexceeding a prescribed value; printed matter exhibiting change in colorwhen viewed from a certain angle (Japanese Unexamined Patent Publication(KOKAI) Heisei No. 5-177919); printed matter imparted with a watermark(latent image) (Japanese Examined Patent Publication (KOKOKU) Heisei No.4-18078, Japanese Unexamined Utility Model Publication (JIKKAI) No.Showa 58-168457); and the like.

[0005] Further, printed matter that has been finely processed to renderreading of the text and images on a copied paper difficult, and warningmarks that appear on a copied paper have been developed (JapaneseUnexamined Utility Model Publication (JIKKAI) No. Showa 59-64271).

[0006] There are also materials that are printed with special magneticink so that an error occurs when a copy is placed on a discriminatingdevice; printed materials that are printed so that the density ofprinted halftones on copies differs from that of the original (authenticnote) (Japanese Examined Patent Publication (KOKOKU) Showa No. 56-19273and Heisei No. 2-51742); and materials on which are printed charactersthat cannot be discerned by the naked eye but on which hidden characterscan be read with a discriminating device (Japanese Unexamined PatentPublication (KOKAI) Showa No. 62-130874).

[0007] Although such a variety of forgery-preventing strategies has beendeveloped, most of the originals can be duplicated by graphicplatemaking, and these forgery-preventing strategies cannot beconsidered complete. Further, many items such as authentic notes developwrinkles during use, and are then rejected by the discriminating deviceas “Unusable”.

[0008] In consideration of these problems of prior art, the presentinvention has for its object to provide a forgery-preventing film thatcan be readily distinguished from copies, tends not to wrinkle, andaffords good print adhesion.

DISCLOSURE OF THE INVENTION

[0009] The present inventors conducted extensive research, resulting inthe discovery that the above-stated object can be achieved by theforgery-preventing film of the present invention which has, on one sideof a first layer (A) comprising a thermoplastic resin, a second layer(B) comprising a thermoplastic resin, and satisfies at least one ofConditions 1 to 4:

[0010] Condition 1: one side of first layer (A) is treated to preventforgery and second layer (B) is formed on the surface of the treatedside of first layer (A);

[0011] Condition 2: second layer (B) comprises at least twothermoplastic resins of different melt viscosities;

[0012] Condition 3: porosity of second layer (B) is greater thanporosity of first layer (A); and

[0013] Condition 4: a polymer net is formed on one side of first layer(A) and second layer (B) is formed on the surface having the polymernet.

[0014] In the forgery-preventing film of the present invention, a thirdlayer (C) is desirably formed on the back side of first layer (A), andfirst layer (A) is desirably of a multilayer structure.

[0015] In the forgery-preventing film of the present inventionsatisfying Condition 1, both sides of first layer (A) are desirablytreated to prevent forgery, with second layer (B) and third layer (C)being formed on the treated surfaces of the first layer (A). It isfurther desirable that the treatment to prevent forgery is embossing orprinting. The opacity of the film used to prevent forgery can beadjusted to from 1 to 60 percent. Additionally, the porosity of firstlayer (A) can be made from 0 to 40 percent and the porosity of secondlayer (B) can be made from greater than 20 percent to less than or equalto 40 percent (referred to hereinafter as Condition 5). In the film forpreventing forgery of the present invention satisfying Condition 5, athird layer (C), having a porosity of greater than 20 percent and lessthan or equal to 40 percent, is desirably formed on the back side offirst layer (A). The opacity is desirably greater than 60 percent andless than or equal to 99 percent.

[0016] In the forgery-preventing film of the present inventionsatisfying Condition 2, the difference in melt viscosity of twothermoplastic resins having different melt viscosities contained insecond layer (B) is desirably greater than 50 Pa·s. A third layer (C)comprising at least two thermoplastic resins having different meltviscosities is desirably formed on the back side of first layer (A).Further, the difference in the melt viscosity of the at least twothermoplastic resins of different melt viscosities contained in thirdlayer (C) is desirably greater than 50 Pa·s.

[0017] Further, the opacity of the forgery-preventing film is desirablyfrom 1 to 60 percent.

[0018] In the forgery-preventing film of the present inventionsatisfying Condition 3, the ratio (A/B) of the porosity of first layer(A) to that of second layer (B) is desirably less than or equal to ⅓.Each of first layer (A) and second layer (B) desirably comprises aninorganic finepowder and/or an organic filler, with an average particlediameter of the inorganic finepowder and/or the organic filler containedin second layer (B) being desirably greater than the average particlediameter of the inorganic finepowder and/or the organic filler containedin first layer (A). Further, a third layer (C) comprising athermoplastic resin is desirably formed on the back side of first layer(A), with the porosity of third layer (C) desirably being greater thanthat of first layer (A). The ratio (A/C) of the porosity of first layer(A) to that of third layer (C) is desirably less than or equal to ⅓. Inparticular, both first layer (A) and third layer (C) desirably comprisean inorganic finepowder and/or an organic filler, with the averageparticle diameter of the inorganic finepowder and/or the organic fillercontained in first layer (C) desirably being greater than the averageparticle diameter of the inorganic finepowder and/or the organic fillercontained in third layer (A). Further, the opacity of theforgery-preventing film is desirably from 10 to 60 percent.

[0019] The forgery-preventing film of the present invention satisfyingCondition 4 is desirably treated to prevent forgery with a polymer net.Further, the forgery-preventing film is desirably stretched in at leastone direction, with the polymer net being desirably comprised of athermoplastic resin and having a network structure in the form of agrid. In particular, the structural component (T) in the traversedirection of the polymer net is desirably an unstretched thermoplasticresin tape. Further, an average traverse and longitudinal tear strengthas described in JIS K7128 is desirably greater than or equal to 20 gf.Still further, a third layer (C) is desirably formed on the back side offirst layer (A). In particular, first layer (A) is desirably treated toprevent forgery on both surfaces, with second layer (B) and third layer(C) being desirably formed on each of the treated sides of first layer(A). Further, the opacity of second layer (B) and third layer (C) isdesirably from 1 to 99 percent.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] The forgery-preventing film of the present invention is describedin detail below with reference to suitable implementation modes.

[0021] The forgery-preventing film of the present invention has astructure in which a second layer (B) is formed on one side of firstlayer (A). Further, a third layer (C) is desirably present on theopposite side of first layer (A). The individual layers constituting theforgery-preventing film of the present invention will be described inorder, along with their methods of manufacture and application.

First Layer (A)

[0022] First layer (A) constituting the forgery-preventing film of thepresent invention, comprises at least a thermoplastic resin.

[0023] Examples of the thermoplastic resin employed in first layer (A)are: high-density polyethylene, medium-density polyethylene, low-densitypolyethylene, and other ethylene based resins; propylene based resins,polymethyl-1-pentene, ethylene-cyclic olefin copolymers, styrene graftedpolyolefin resins, and other polyolefin resins; nylon 6, nylon 6,6,nylon 6,10, nylon 6,12, and other polyamide resins; polyethyleneterephthalate and copolymers thereof, polyethylene naphthalate,aliphatic polyester and other thermoplastic polyester resins; andpolycarbonates, atactic polystyrene, syndiotactic polystyrene,polyphenylenesulfide, and other thermoplastic resins. Two or more ofthese compounds may be combined for use. Of these, the use of polyolefinresins is preferred. Among the polyolefin resins, from the perspectivesof cost, water resistance, and chemical resistance, the use of propylenebased resin and high-density polyethylene is preferred.

[0024] The propylene based resin employed is desirably a propylenehomopolymer (polypropylene) exhibiting isotactic, syndiotactic or somedegree of stereoregularity, metallocene propylene, or copolymercomprising a principal component in the form of propylene with ethylene,1-butene, 1-hexene, 1-heptene, 4-methyl-1-pentene, or some otherα-olefin. These copolymers may be two-component, three-component, orfour-component systems, as well as random copolymers or blockcopolymers.

[0025] In addition to a thermoplastic resin, first layer (A) alsodesirably comprises an inorganic finepowder and/or an organic filler.

[0026] An inorganic finepowder with an average particle diameter of from0.01 to 15 micrometers, preferably from 0.01 to 8 micrometers, and morepreferably, from 0.03 to 4 micrometers may be employed. Specifically,calcium carbonate, calcined clay, silica, diatomaceous earth, talc,titanium dioxide, barium sulfate, alumina, or the like may be employed.

[0027] An organic filler with an average particle diameter followingdispersion of from 0.01 to 15 micrometers, preferably from 0.01 to 8micrometers, and more preferably from 0.03 to 4 micrometers may beemployed. A resin differing from the thermoplastic resin that is theprincipal component is desirably selected as the organic filler. Forexample, when the thermoplastic resin is a polyolefin resin, the organicresin for the organic filler is desirably polyethylene terephthalate,polybutylene terephthalate, polycarbonate, nylon 6, nylon 6,6, cyclicolefin homopolymer, or the copolymer of a cyclic olefin and ethylene,having a melting point of from 120 to 300° C. or a glass transitiontemperature of from 120 to 280° C.

[0028] As needed, stabilizers, photostabilizers, dispersing agents,lubricants, fluorescent whitening agents, colorants, and the like mayalso be blended into first layer (A).

[0029] For example, 0.001 to 1 weight percent of a steric hinderedphenol-based, phosphorus-based, or amine-based stabilizer may be blendedin as the stabilizer. For example, 0.001 to 1 weight percent of a sterichindrance amine, benzotriazole-based, benzophenone-based, or otherphotostabilizer may be blended in as the photostabilizer. For example,0.01 to 4 weight percent of a silane coupling agent, a higher aliphaticacid such as oleic acid or stearic acid, a metal soap, polyacrylic acid,polymethacrylic acid, or salts thereof may be blended in as thedispersing agent of the inorganic finepowder. For example, 0.001 to 1weight percent of imidazole, imidazolone, triazole, thiazole, oxazole,oxadiazole, cumarin, carbostyryl, thiadiazole, napthylimido, orpyrazolone may be blended in as the fluorescent whitening agent;specific examples are 2,5-bis[5-t-butylbenzooxazolyl(2)]thiophene,dicyclohexyl phthalate, 4-methoxynaphthalic acid-N-methylimide,diaminostylbenedisulfonic acid derivatives, and diaminostylbenederivatives. Pellets that have been colored with various pigments may beblended in a proportion of 5 to 30 weight percent as coloring agents.

[0030] First layer (A) of the forgery-preventing film of the presentinvention may have a single-layer structure or a multilayer structure oftwo layers or more. First layer (A) or a portion of a layer comprisingfirst layer (A) is desirably stretched in at least one direction.

[0031] When first layer (A) is comprised of a three-layer structure(A1/A2/A3) of layer (A1), layer (A2), and layer (A3), the thickness of(A1+A3) is desirably greater than or equal to 1 micrometer, and theratio of the thickness of (A1+A3) to A2 is desirably from 1:40 to 1:10.The thickness of first layer (A) is desirably from 25 to 100micrometers, preferably from 30 to 75 micrometers, and more preferablyfrom 40 to 60 micrometers.

[0032] In the forgery-preventing film of the present invention thatsatisfies Condition 1, one or both sides of first layer (A) is treatedto prevent forgery. The treatment to prevent forgery may be a directtreatment of the surface of first layer (A), or a layer that has beentreated to prevent forgery may be formed over first layer (A). Theembossing or printing of the surface of first layer (A) is preferred.

[0033] As examples of methods of embossing, various known presses andembossers such as planographic presses and roll embossers may be used toraise in relief the design of an embossing plate by means of heat andpressure. In the roll embossing method, the relief design of anembossing drum is imparted by heat and pressure to the material beingembossed. As a specific example, first layer (A) is extruded in hot meltform as a film from a single-layer or multilayer T-die or I-dieconnected to an extruder and then cooled by cooling rolls to obtain afilm. In the course of this process, the film surface is pressed withembossing rolls to impart a shape and cooled to fix the shape.

[0034] Portions of the film that contact raised areas of the embossingrolls during this process are whitened during stretching. Further, thefilm is misted by blowing water in mist form to rapidly cool portions ofthe film with water droplets and cause them to turn white. Followingcooling of first layer (A), a shape may also be stamped with hot rolls.

[0035] Various printing methods, such as hot melt transfer,electrophotography, ink-jet, and laser marker, may be employed in thetreatment to prevent forgery. In particular, when printing a wax-type orresin-type ink used in the hot melt transfer method, the image is firsttransferred to a film with weak ink adhesion, a heating roll or the likeis employed from the back of the print surface of this film to bringabout hot pressure adhesion to the unstretched film, therebytransferring the image. Accordingly, with this method, it is possiblenot to provide a printing device in the molding line.

[0036] Treatment to prevent forgery by printing is desirably conductedwhile first layer (A) is in an unstretched state prior to stretching.When first layer (A) is being uniaxially stretched, printing isconducted before longitudinal stretching, and when it is being biaxiallystretched, printing is conducted before longitudinal or traversestretching.

[0037] In one form of treatment to prevent forgery of Condition 1, alayer that has been treated to prevent forgery is sandwiched betweenfirst layer (A) and second layer (B), and/or between first layer (A) andthird layer (C). The layer that has been treated to prevent forgery maybe a printed layer, for example. For example, the layer that has beentreated to prevent forgery may be deposited following stretching offirst layer (A) and then sandwiched in by forming second layer (B) orthird layer (C) thereover. When preparing a forgery-preventing filmcomprising, for example, a uniaxially stretched second layer (B), abiaxially stretched first layer (A), and a uniaxially stretched thirdlayer (C), following the longitudinal stretching of layer (A) andimmediately before the hot melt lamination of layer (B), a preprintedfilm (D) may be inserted to obtain a forgery-preventing film in the formof a (B)/(D)/(A)/(D)/(B) or (B)/(D)/(A)/(B) laminate.

[0038] Printed film (D) may be an unstretched film, a uniaxiallystretched film, a biaxially stretched film, or a laminate thereof, but auniaxially stretched film is preferred from the perspective ofpreventing increased traverse stretching stress in subsequentprocessing. Methods of printing include electrophotographic methods, hotmelt transfer, and rewritable marking. An ink-jet printer may beemployed, as may letterpress printing, gravure printing, flexo printing,solvent offset printing, ultraviolet-setting offset printing, offsetprinting, screen printing and various other forms of printing. Theprinted image is desirably reduced in size by 1/(stretching ratio) inconsideration of the subsequent stretching ratio.

[0039] Hot marking the forgery-preventing film satisfying Condition 1 isalso possible to prevent forgery. When the opacity of theforgery-preventing film is made a low 1 to 60 percent, the opacity ofportions that have been hot marked decreases, rendering themsemitransparent or transparent. Portions that are not pressed during hotmarking retain their original semitransparency so that when exposed tosunlight or a light source such as a fluorescent lamp, a sharp mark isobtained and forgeries can be detected at a glance. However, unclearmarks are obtained in fully transparent films, and it tends to bedifficult to detect forgeries at a glance. Further, when a largequantity of inorganic finepowder and/or organic filler is incorporated,when mark pressing is conducted at ordinary temperature, in contrast tohot marking, voids within the film are crushed and the crushed areasbecome opaque, with areas outside the pressed areas remainingsemitransparent. It is thus possible to obtain a sharp mark permittingthe detection of forgeries at a glance.

[0040] When the opacity of the forgery-preventing film is greater than60 percent and less than or equal to 99 percent, such as when Condition5 is satisfied, the pressed portions become less opaque during hotmarking, becoming semitransparent or transparent. Portions that are notpressed during hot marking retain their original opacity, so that whenexposed to sunlight or a light source such as a fluorescent lamp, asharp mark can be recognized, permitting the detection of forgeries at aglance. However, the marks become unclear in completely transparentfilms, and it tends to be difficult to detect forgeries at a glance.

[0041] The marking step with heating or at ordinary temperature not onlyhas the effect of preventing forgery, but also effectively permitspersons with impaired vision to readily determine the denomination of abill or the like by feeling it with the finger tips.

Polymer Net

[0042] In the forgery-preventing film of the present inventionsatisfying Condition 4, a polymer net is laminated on one side of firstlayer (A), and second layer (B) is laminated over the surface on whichthe polymer net has been laminated.

[0043] The method of treating the polymer net to prevent forgery is notspecifically limited. For example, a printed layer may be provided on athermoplastic resin film, a fluorescent whitening agent or a fluorescentpigment may be kneaded in, or two or more of such methods may beemployed in combination. When printing is employed, for example, atrademark, code, mark, patent number, publisher, producer, materialname, product number, product specification number, lot number, barcode, or the like may be printed. The size of the print is desirablysmaller than the width of the thermoplastic resin tape constituting thepolymer net and large enough to permit reading without missing print inthe case of a polymer net. Specifically, the print desirably fallswithin a range of from 0.5 to 2 mm.

[0044] Methods of printing include electrophotographic methods, hot melttransfer, rewritable marking, and ink-jet printer. Letterpress printing,gravure printing, flexo printing, solvent offset printing,ultraviolet-setting offset printing, offset printing, screen printingand various other forms of printing may be employed. The printed imageis desirably reduced in size by 1/(stretching ratio) in consideration ofthe subsequent stretching ratio.

[0045] The ink employed in printing of the printed layer is notspecifically limited. Common commercially employed inks may be employed.To better prevent forgery, fluorescent ink, phosphorescent ink, metallicink, photochromic ink, thermochromic ink, holographic ink, bubble ink,and other special inks are desirably employed. A thermosetting, e-beamsetting, or ultraviolet setting resin is desirably employed as thebinder.

[0046] The thermosetting resin film having a printed layer may be cutusing a known microslitter or tape slitter to obtain a thermoplasticresin tape for use in the polymer net. Cutting is desirably conducted inunprinted portions. The width of the thermoplastic resin tape is notspecifically limited, but is normally about 1 to 5 mm.

[0047] There are no restrictions in the running direction or traversedirection of the thermoplastic resin tape. Woven cloth may be obtainedby a known weaving machine manufacturing method or by hot melt bondingstrands of tape together into a grid. The method of weaving whenemploying a weaving machine is not specifically limited; plain weavingand twill weaving are both acceptable.

[0048] On the forgery-preventing film satisfying Condition 4, it is alsopossible to conduct hot marking to prevent forgery. When the opacity ofthe forgery-preventing film of the present invention is made high, atgreater than 60 percent and less than or equal to 99 percent, theopacity of areas that are pressed during processing decreases during hotmelt marking, becoming semitransparent or transparent. Areas that arenot pressed during hot melt marking retain their original opacity, sothat when exposed to sunlight or a light source such as a fluorescentlamp, the mark can be clearly discerned and forgeries can be detected ata glance. However, in totally transparent films, the marks becomeunclear, tending to make it difficult to determine forgeries at aglance.

[0049] This hot marking affords not only the above-describedforgery-preventing effect, but also effectively permits persons withimpaired vision to readily determine the denomination of a bill or thelike by feeling it with the finger tips.

[0050] One of the above-described forgery-preventing treatment methodsmay be selected, or two or more may be selected for use in combinationin the forgery-preventing film of the present invention. When one methodis selected, a good forgery-preventing effect can be imparted relativelyinexpensively. When two or more methods are selected for use incombination, more effective forgery prevention can be achieved.

Second Layer (B) and Third Layer (C)

[0051] A second layer (B) is formed on one side of first layer (A)constituting the forgery-preventing film of the present invention. Athird layer (C) is also formed, desirably on the opposite side of firstlayer (A).

[0052] Second layer (B) and third layer (C) both contain thermoplasticresins. Second layer (B) and third layer (C) also desirably contain aninorganic finepowder and/or organic filler. The thermoplastic resin,inorganic finepowder, and organic filler employed in second layer (B)and third layer (C) may be identical to those employed in first layer(A).

[0053] As needed, stabilizers, photostabilizers, dispersing agents,lubricants, fluorescent whitening agents, colorants, and the like mayalso be blended into second layer (B) and third layer (C).

[0054] Second layer (B) and third layer (C) may each have a single-layerstructure or a multilayer structure of two or more layers. One or moreof the layers comprising second layer (B) and third layer (C) isdesirably stretched in at least one axial direction. The thickness ofsecond layer (B) and third layer (C) is desirably from 5 to 50micrometers, preferably from 10 to 40 micrometers each. However, whenCondition 5 is satisfied, the thickness of second layer (B) and thirdlayer (C) is desirably 10 to 50 micrometers, preferably 15 to 40micrometers each.

[0055] In the forgery-preventing film of the present invention, thestructure is desirably one where second layer (B) and third layer (C)are formed on either side of first layer (A). A forgery-preventing filmin which first layer (A) comprises 40 to 99.5 weight percent ofpolyolefin resin and 60 to 0.5 weight percent of an inorganic finepowderand/or organic filler, and second layer (B) and third layer (C) comprisefrom 25 to 100 weight percent polyolefin resin and from 75 to 0 weightpercent inorganic finepowder and/or organic filler is particularlydesirable. A forgery-preventing film in which first layer (A) comprisesfrom 50 to 97 weight percent polyolefin resin and from 50 to 3 weightpercent inorganic finepowder and/or organic filler, and second layer (B)and third layer (C) comprise from 30 to 97 weight percent polyolefinresin and from 70 to 3 weight percent inorganic finepowder is furtherdesirable. However, when the forgery-preventing film of the presentinvention satisfies Condition 5, a forgery-preventing film in whichfirst layer (A) comprises from 40 to 99.5 weight percent polyolefinresin and from 60 to 0.5 weight percent inorganic finepowder and/ororganic filler, and second layer (B) and third layer (C) comprise from25 to 85 weight percent polyolefin resin and from 75 to 15 weightpercent inorganic finepowder and/or organic filler is desirable.Further, a forgery-preventing film in which first layer (A) comprisesfrom 50 to 97 weight percent polyolefin resin and from 50 to 3 weightpercent inorganic finepowder and/or organic filler, and second film (B)and third film (C) comprise from 30 to 80 weight percent polyolefinresin and from 70 to 20 weight percent inorganic finepowder ispreferred.

[0056] When the quantity of inorganic finepowder and/or organic fillercontained in first layer (A) exceeds 60 weight percent, the stretchedresin film tends to rupture during traverse stretching followinglongitudinal stretching. When the quantity of inorganic finepowderand/or organic filler in second layer (B) and third layer (C) exceeds 75weight percent, the surface strength of second layer (B) and third layer(C) following traverse stretching weakens, and second layer (B) andthird layer (C) tend to be damaged by mechanical impact during use.

[0057] Other layers may be provided between first layer (A) and secondlayer (B) comprising the forgery-preventing film of the presentinvention, between first layer (A) and third layer (C), on second layer(B), and on third layer (C).

[0058] In the forgery-preventing film of the present inventionsatisfying Condition 2, second layer (B) comprises at least twothermoplastic resins of differing hot melt viscosity. In the presentSpecification, the term “hot melt viscosity” refers to the hot meltviscosity at 230° C. at a shear rate of 1,220 s⁻¹. Here, the differencein hot melt viscosity of the two thermoplastic resins of differing holtmelt viscosity contained in second layer (B) is desirably greater than50 Pa·s, preferably greater than or equal to 70 Pa·s, and morepreferably, greater than or equal to 80 Pa·s. Third layer (C) alsosimilarly contains at least two thermoplastic resins of differing hotmelt viscosity, with the difference in hot melt viscosity of the twothermoplastic resins of differing holt melt viscosity being desirablygreater than 50 Pa·s, preferably greater than or equal to 70 Pa·s, andmore preferably, greater than or equal to 80 Pa·s. Making the differencein hot melt viscosity greater than 50 Pa·s permits the adequateformation of streaks in the flow generated during extrusion filmmolding. These streaks can be used to effectively prevent forgery.

[0059] The combination of thermoplastic resins of differing hot meltviscosity is not specifically limited. The thermoplastic resins employedin above-described first layer (A) may be suitably combined for use.Specifically, the use of a combination of a propylene homopolymer and anethylene based resin, or a propylene homopolymer and a styrene graftpolyolefin resin is preferred. The thermoplastic resin of higher hotmelt viscosity desirably has a hot melt viscosity of from 180 to 300Pa·s, with from 200 to 280 Pa·s being preferred. The thermoplastic resinof lower hot melt viscosity desirably has a hot melt viscosity of from50 to 130 Pa·s, with from 60 to 120 Pa·s being preferred.

[0060] When manufacturing the forgery-preventing film of the presentinvention satisfying Condition 3, the average particle diameter of theinorganic finepowder employed in second layer (B) and third layer (C) isnormally from 2 to 30 micrometers, preferably from 3 to 20 micrometers,and more preferably from 3 to 15 micrometers. The average particlediameter following dispersion of the organic filler employed in secondlayer (B) and third layer (C) is normally from 2 to 30 micrometers,preferably from 3 to 20 micrometers, and more preferably from 3 to 15micrometers. And the average particle diameter of the inorganicfinepowder and/or organic filler employed in second layer (B) and thirdlayer (C) is desirably greater than the average particle diameter of theinorganic finepowder and/or organic filler employed in first layer (A).

Manufacturing and Processing of the Forgery-preventing Film

[0061] The forgery-preventing film of the present invention can bemanufactured by combining various methods known to those skilled in theart. A forgery-preventing film manufactured by whatever method onlyfalls within the scope of the present invention if it satisfies theconditions stated in the claims below.

[0062] An example of a conventional method is to conduct stretchingafter the formation of the layers constituting the forgery-preventingfilm.

[0063] The forming method is not specifically limited; any known methodmay be employed. Specifically, a single-layer or multilayer T-die orI-die connected to a screw extruder may be employed to extrude the hotmelt resin into film form by cast molding, calender molding, rolling,inflation molding, cast molding or calendering of a mixture ofthermoplastic resin and organic solvent or oil followed by removal ofthe solvent or oil, molding from a solution of thermoplastic resin,molding by solvent removal, or the like.

[0064] The stretching method is not also specifically limited; any ofvarious known methods may be employed. Specific examples of stretchingmethods are: stretching between rolls exploiting the difference inperipheral speed of a group of rolls and clip stretching exploiting atenter oven. More specifically, longitudinal stretching exploiting thedifference in peripheral speed of a group of rolls, traverse stretchingemploying a tenter oven, rolling, and simultaneous biaxial stretching bya combination of a tenter oven and a linear motor may be employed. Thestretching of each layer may be uniaxial, biaxial, or greater. Forexample, when manufacturing a film comprised of a three-layer structureconsisting of second layer (B)/first layer (A)/third layer (C), thedegrees of stretching of each layer may be any combination, such asuniaxial/biaxial/uniaxial, uniaxial/uniaxial/uniaxial, orbiaxial/biaxial/biaxial.

[0065] The stretching ratio is not specifically limited, and may besuitably selected based on the objective and the characteristics of thethermoplastic resin employed. For example, when employing a propylenehomopolymer or a copolymer thereof as the thermoplastic resin, duringuniaxial stretching, a ratio of about 1.2 to 12-fold is desirable, with2 to 10-fold preferred. During biaxial stretching, an area ratio of from1.5 to 60-fold is desirable, with from 10 to 50-fold being preferred.When employing other thermoplastic resins, during uniaxial stretching, aratio of from 1.2 to 10-fold is desirable, with from 2 to 5-fold beingpreferred. During biaxial stretching, a surface area ratio of from 1.5to 20-fold is desirable, with from 4 to 12-fold being preferred. Asneeded, a heat treatment may be applied at elevated temperature.

[0066] Drawing is conducted within a suitable known temperature range ofgreater than or equal to the glass transition temperature when anamorphous resin is employed and from greater than or equal to the glasstransition temperature of the amorphous component and less than or equalto the crystal melting temperature of the crystalline portion when acrystalline resin is employed. Generally, stretching is desirablyconducted at a temperature of from 2 to 60° C. lower than the meltingpoint of the thermoplastic resin employed. When employing athermoplastic resin in the form of a propylene homopolymer (with amelting point of from 155 to 167° C.), stretching is desirably conductedat from 152 to 164° C., when employing high-density polyethelene (with amelting point of from 121 to 134° C.), stretching is desirably conductedat 110 to 120° C., and when employing polyethylene terephthalate (with amelting point of from 246 to 252° C.), stretching is desirably conductedat from 104 to 115° C.

[0067] Further, a stretching rate of from 20 to 350 m/min is desirable.

[0068] The order of lamination and stretching of the individual layerscomprising the forgery-preventing film of the present invention is notspecifically limited. For example, first layer (A) and second layer (B)may be separately stretched and then laminated, or first layer (A) andsecond layer (B) may be laminated and then collectively stretched. Whenthird layer (C) is present, the three layers may be separately stretchedand then laminated, laminated first and then collectively stretched, orfirst layer (A) and third layer (C) may be laminated and stretched,after which stretched or unstretched second layer (B) may be laminatedto manufacture the forgery-preventing film of the present invention.These methods may also be suitably combined.

[0069] The preferred manufacturing method is to first laminate multiplelayers and then conduct stretching collectively. Greater convenience isafforded and the cost is lower than when each layer is separatelystretched and then laminated.

[0070] When an inorganic finepowder and/or organic filler is containedin the layers, stretching causes fine cracking of the film surface, withfine voids being produced in the film. The porosity of theforgery-preventing film of the present invention following stretching isfrom 1 to 20 percent, preferably from 2 to 15 percent, when it isdesirable to suppress opacity in a forgery-preventing film satisfyingCondition 1. The same is true for forgery-preventing films satisfyingConditions 2, 3, and 4.

[0071] In a forgery-preventing film satisfying Condition 3, the porosityof second layer (B) is made greater than that of first layer (A). Theuse of such a configuration makes clear the presence of voidsnonuniformly distributed within second layer (B) or produces whitepattern in the second layer (B) that effectively prevent forgery. Toeffectively generate white pattern, it is desirable to keep the porosity(A/B) of first layer (A) to second layer (B) to less than or equal to ⅓.In a forgery-preventing film of the present invention comprising thirdlayer (C), the porosity of third layer (C) is desirably made greaterthan that of first layer (A), with the porosity (A/C) being kept to lessthan or equal to ⅓.

[0072] In a forgery-preventing film satisfying Condition 5, therespective porositys of first layer (A), second layer (B), and thirdlayer (C) are desirably from 0 to 40 percent, greater than 20 percentand less than or equal to 40 percent, and greater than 20 percent andless than or equal to 40 percent, with respective porositys of from 1 to30 percent, 25 to 35 percent, and 25 to 35 percent being preferred. Wheneach of these exceeds 40 percent, the forgery-preventing treatmentbecomes difficult to make out with transmitted light.

[0073] To improve the antistatic property and suitability to variousforms of printing of the thermoplastic resin layer comprising theoutermost layer of the forgery-preventing film of the present invention,a surface treatment is desirably conducted to modify the surfacefollowing molding of the laminate structure. An example of a surfacetreatment method is the combination of a surface oxidation treatment andtreatment with a surface treatment agent.

[0074] The surface oxidation treatment may be conducted by the use,either singly or in combination, of generally employed corona dischargetreatment, flame treatment, plasma treatment, glow discharge treatment,ozone treatment, or the like. Of these, the corona treatment and flametreatment are preferred. The corona treatment level is desirably from600 to 12,000 J/m² (10 to 200 W·min/m²), with from 1,200 to 9,000 J/m²(20 to 150 W·min/m²) being preferred. The flame treatment is desirablyconducted at from 8,000 to 200,000 J/m², with from 20,000 to 100,000J/m² being preferred.

[0075] The surface treatment agent may be selected chiefly from amongthe following primers and antistatic polymers, and may thus be a singlecompound or a mixture of two or more components. From the perspective ofpreventing static and improving adhesion in a dry laminate, thepreferred surface treatment agent is a primer or a combination of primerand antistatic polymer.

[0076] Examples of primers constituting surface treatment agentssuitable for use are: polyethyleneimine, polyethyleneimines modifiedwith alkyls having from 1 to 12 carbon atoms, ethyleneimine adducts ofpoly(ethyleneimine-urea) and polyaminepolyamide and epichlorhydrinadducts of polyamine polyamides, and other polyethyleneimine polymers;acrylic acid amide-acrylic acid ester copolymers; acrylic acidamide-acrylic acid ester-methacrylic acid ester copolymers,polyacrylamide derivatives, oxazoline group-comprising acrylic acidester polymers, polyacrylic acid esters, and other acrylic acid esterpolymers; polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol,and other water-soluble resins; and polyvinyl acetate, polyurethane,ethylene-vinyl acetate copolymers, polyvinylidene chloride,polypropylene chloride, acrylonitrile-butadiene copolymers, and otherwater-dispersible resins.

[0077] Of these, the compounds of preference are the polyethyleneiminepolymers, urethane resins, and polyacrylic acid esters. The compounds ofgreater preference are the polyethyleneimine polymers. And the compoundsof even greater preference are polyethyleneimines having a degree ofpolymerization of from 20 to 3,000, the ethyleneimine adducts ofpolyamine polyimides, and modified polyethyleneimines obtained bymodifying these compounds with alkyl halides having from 1 to 24 carbonatoms, alkenyl halides having from 1 to 24 carbon atoms, cycloalkylhalides having from 1 to 24 carbon atoms, and halogenated benzyl groupshaving from 1 to 24 carbon atoms.

[0078] Examples of antistatic polymers comprising surface treatmentagents are cationic polymers, anionic polymers, and amphoteric polymers.Examples of cationic polymers are polymers having quaternary ammoniumsalt or phosphonium salt structures, nitrogenous acrylic polymers, andnitrogenous acrylic or methacrylic polymers having a quaternary ammoniumsalt structure. Examples of amphoteric polymers are nitrogenous acrylicor methacrylic polymers having a betaine structure. Examples of cationicpolymers are styrene-maleic anhydride copolymers and their alkali metalsalts, alkali metal salts of ethylene-acrylic acid copolymers, andalkali metal salts of ethylene-methacrylic acid copolymers. Ofparticular preference are nitrogenous acrylic or methacrylic polymershaving a quaternary ammonium salt structure.

[0079] The molecular weight of the antistatic polymer may be adjusted asdesired based on the polymerization temperature, the type and quantityof polymerization initiator employed, the quantity of solvent employed,the chain-transfer agent employed, and other polymerization conditions.The molecular weight of the polymer obtained is generally from about1,000 to 1,000,000, with a range of from 1,000 to 500,000 beingpreferred.

[0080] The surface treatment agent employed in the present invention maycomprise as needed a crosslinking agent, alkali metal salt, alkalineearth metal salt, or the like.

[0081] The addition of a crosslinking agent to the surface treatmentagent further improves coating strength and water resistance. Examplesof crosslinking agents are glycidyl ether, glycidyl ester, and otherepoxy compounds; epoxy resin; and isocyanate-based, oxazoline-based,formalin-based, and hydrazide-based water-dispersible resins. Thequantity of crosslinking agent added normally falls within a range ofless than or equal to 100 weight parts per 100 weight parts of theactive components, excluding solvent, of the surface-modifying agent.

[0082] Examples of the alkali metal salts and alkaline earth metal saltsemployed in the surface treatment agent are water-soluble inorganicsalts such as sodium carbonate, sodium bicarbonate, potassium carbonate,sodium sulfite, and other alkali salts; and sodium chloride, sodiumsulfate, sodium nitrate, sodium tripolyphosphate, sodium pyrophosphate,ammonium alum, and the like. The quantity added is normally less than orequal to 50 weight parts per 100 weight parts of the active components,excluding solvent, of the surface-modifying agent.

[0083] Surfactants, antifoaming agents, water-soluble andwater-dispersible finepowder substances, and other adjuvants may beadded to the surface-modifying agent. The quantity of these componentsis normally less than or equal to 20 weight parts per 100 weight partsof the active components, excluding solvent, of the surface-modifyingagent.

[0084] The individual components of these surface treatment agents maybe dissolved for use in water or a hydrophilic solvent such as methylalcohol, ethyl alcohol, or isopropyl alcohol. Of these, use in the formof an aqueous solution is conventional. The concentration of the aqueoussolution is normally from 0.1 to 20 weight percent, desirably from about0.1 to 10 weight percent.

[0085] Coating may be conducted by roll coater, blade coater, barcoater, air-knife coater, size press coater, gravure coater, reversecoater, die coater, lip coater, spray coater, or the like. As required,smoothing may be conducted and a drying step may be employed to removeexcess water or hydrophilic solvent.

[0086] The coating amount is 0.005 to 5 g/m², desirably 0.01 to 2 g/m²,based on dry components.

[0087] The surface treatment may be conducted either before or afterlongitudinal or traverse stretching. The surface treatment agent may beapplied in a single application or in a multistage application.

[0088] Following the surface treatment, as needed, awritability-imparting layer, print quality-enhancing layer, heattransfer receiving layer, heat-sensitive recording layer, ink-jetreceiving layer, or the like may be applied by the same method as usedto apply the surface treatment agent.

[0089] When layers are formed on or over the surface of second layer (B)or third layer (C) in the forgery-preventing film of the presentinvention obtained as set forth above, a recording layer may be providedon the surface of the outermost layer. This recording layer may beprinted by electrophotography, sublimation heat transfer, hot melt heattransfer, direct thermal, rewritable marking, ink-jet printer,letterpress printing, gravure printing, flexo printing, solvent offsetprinting, ultraviolet-setting offset printing, or a rotary method basedon the form of the film or a roller.

[0090] One or a combination of two or more of the above-describedforgery-preventing treatments may be applied to the forgery-preventingfilm of the present invention. When one such treatment is applied, agood forgery-preventing effect is achieved relatively inexpensively.When two or more are combined, a better forgery-preventing effect isachieved.

Application of the Forgery-preventing Film of the Present Invention

[0091] The physical properties of the forgery-preventing film of thepresent invention can be suitably adjusted based on the purpose andenvironment of use.

[0092] In films satisfying Condition 1, where it is desirable to keepthe opacity low, the opacity (JIS P8138) of the forgery-preventing filmof the present invention is desirably from 1 to 60 percent, preferablyfrom 5 to 55 percent, and more preferably from 15 to 50 percent. Whenthe opacity exceeds 60 percent, the printing and white pattern producedby embossing of first layer (A) become unclear, tending to compromisethe ability to prevent forgery. In forgery-preventing films satisfyingCondition 2, the same range of opacity is desirable. When the opacityexceeds 60 percent, the streaks formed in second layer (B) and thirdlayer (C) become unclear, tending to compromise the ability to preventforgery.

[0093] In forgery-preventing films satisfying Condition 3, the opacityis desirably from 10 to 60 percent, preferably from 15 to 55 percent,and more preferably from 20 to 50 percent. When the opacity exceeds 60percent, the white pattern formed on second layer (B) and third layer(C) become unclear, tending to compromise the ability to preventforgery. When opacity is less than 10 percent, the low number of voidsand the unclear generation of white pattern in second layer (B) andthird layer (C) tend to compromise the ability to prevent forgery. Inforgery-preventing films satisfying Condition 4, the opacity isdesirably from 1 to 99 percent, preferably from 5 to 97 percent, andmore preferably from 15 to 95 percent. When the opacity exceeds 99percent, the printing and fluorescent dyes applied to the polymer netare unclear, tending to compromise the ability to prevent forgery. Inforgery-preventing films satisfying Condition 5, the opacity isdesirably greater than 60 percent and less than or equal to 99 percent,preferably from 65 to 97 percent, and more preferably from 70 to 95percent. When the opacity exceeds 99 percent, the printing and whitepattern formed by embossing on first layer (A) become visible whenviewed either by reflected light or transmitted light, tending tocompromise the ability to prevent forgery. Further, at less than orequal to 60 percent, the printing and white pattern formed by embossingof first layer (A) become unclear when viewed with reflected light,tending to compromise the ability to prevent forgery.

[0094] Further, the whiteness (JIS L1015) of the forgery-preventing filmof the present invention is desirably 60-100 percent, preferably 70 to100 percent. When the whiteness is outside this range, images andcharacters printed on second layer (B), third layer (C), and theoutermost layer become unclear and difficult to recognize, and theexternal appearance tends to become unappealing.

[0095] The thickness of the forgery-preventing film of the presentinvention is desirably 50 to 200 micrometers, preferably 60 to 150micrometers, and more preferably 80 to 120 micrometers. At a thicknessof less than 50 micrometers, strength is inadequate and durabilitydeteriorates. When a thickness of 200 micrometers is exceeded, banknotes (paper money) become excessively stiff and tend to be difficult tohandle.

[0096] The tear strength (JIS K7128) of the forgery-preventing film ofthe present invention satisfying Condition 5 is desirably greater thanor equal to 20 gf as an average longitudinal and traverse value. Whenthe tear strength is outside this range, for example, in bank notesemploying the present invention, tearing tends to begin at notches andscratches produced by circulation, tending to cause problems in thefeeding of paper in automatic vending machines and the like.

[0097] These physical properties can be adjusted by suitably combiningknown methods.

[0098] Since first layer (A) is treated to prevent forgery in theforgery-preventing film of the present invention, the advantage of beingable to readily detect copies is afforded.

[0099] For example, when a real bill that has been produced with anembossed forgery-preventing film satisfying Condition 1, or aforgery-preventing film satisfying Condition 2 or 3, is copied withsilver salt photographic paper, thermal transfer image receiving paper,an OHP sheet comprised of polyethylene terephthalate biaxially stretchedfilm, or the like, when the pressing cover of the copier is made ofaluminum, the semitransparent portions of the real bill are printedbluish black in the copy. Thus, the two are readily distinguished by avisual comparison of the semitransparent portions of the real bill andthe copy. When the pressing cover of the copier is a white plasticplate, cloth, or white cardboard, the pattern and white stripes in thewatermark portions of the real bill end up becoming the color of thepaper on the copy and are lost, and become transparent and are lost oncopied OHP film. Thus, a visual comparison of the watermark portions ofthe original bill and the copy reveals the presence or absence of thepattern and white stripes, permitting ready distinction of the two.

[0100] When a real bill that has been produced with a forgery-preventingfilm satisfying Condition 1 that has been printed to prevent forgery iscopied, the contrast of the copied image of the printed portion of thereal bill changes greatly. The image is no longer sharp, and densitydecreases. Thus, a visual comparison of the sharpness of the image ofthe real bill and the copy permits the ready distinction of the two.

[0101] To reliably achieve the forgery-preventing effect of theforgery-preventing film of the present invention, it is desirable tointentionally provide portions (watermarks) where the recording layerremains unprinted.

[0102] When a real bill that has been produced using aforgery-preventing film satisfying Condition 4 is copied, the gridpattern of the polymer net is not copied. Further, although printing onthe polymer net is copied, the contrast and resolution of the copiedimage are quite different. Thus, the image becomes unclear and thedensity decreases. Further, in bills that have been processed to preventforgery with fluorescent ink and fluorescent whitening agents, thefluorescent colors cannot be reproduced or copying is altogetherprecluded. Thus, the real item and the forgery can be readilydistinguished. Further, when photochromic ink is employed as theabove-described special ink, the printed pattern of the photochromicportion can be viewed when exposed to ultraviolet radiation in the formof a black light or the like although the printed pattern can not beviewed under white light. When a fluorescent pigment is employed as thespecial ink, the printed pattern of the fluorescent pigment can beviewed under white light and ultraviolet radiation.

[0103] Even when the fluorescent ink portion is copied without copyingthe photochromic portion, exposure to ultraviolet radiation in the formof a black light permits the distinction of real and forged items.

[0104] Forgery-preventing films satisfying Condition 5 are treated toprevent forgery so that the treatment of first layer (A) cannot be seenwith reflected light, but must be viewed with transmitted light. Thus,the forgery-preventing treatment cannot be copied. A further advantageis afforded in that even were such a treatment to be copied, the copyingwould be readily apparent.

[0105] The forgery-preventing film of the present invention can bebroadly applied to any item the forging of which must be prevented.Examples are bank notes, bills, checks, traveler's checks, lotterytickets, product certificates, stock certificates, other securities,various cards, entry tickets, tickets, national identity cards, driver'slicenses, resident cards, household registers, official stampcertificates, passports, visas, deposit certificates, and pledgecertificates. When the forgery-preventing film of the present inventionis employed to make paper money, the appearance of the original simplepaper bill is maintained without any sense of incompatibility.Water-repellency and durability are good, and numerous applications arepossible.

EXAMPLES

[0106] The characteristics of the present invention are specificallydescribed below through examples. The materials, quantities employed,ratios, treatments, treatment sequences, and the like indicated in theexamples below may be suitably modified while remaining within thespirit of the present invention. Accordingly, the scope of the presentinvention is not to be interpreted as being limited to these specificexamples.

Example 1

[0107] Composition (A) was prepared by mixing 87 weight parts ofpropylene homopolymer with a melt flow rate (MFR) of 4 g/10 min, 3weight parts of heavy calcium carbonate with an average particlediameter of 3 micrometers, 10 weight parts of high-density polyethylenewith an MFR of 10 g/10 min, 0.05 weight part of3-methyl-2,6-di-t-butylphenol per a total of 100 weight parts of thepropylene homopolymer and the heavy calcium carbonate, 0.08 weight partof phenol stabilizer (made by Ciba-Geigy Co., product name Irganox 1010)per a total of 100 weight parts of the propylene homopolymer and theheavy calcium carbonate, and 0.05 weight part of phosphorus-basedstabilizer (made by G. E. Plastics, product name Weston 618) per a totalof 100 weight parts of the propylene homopolymer and the heavy calciumcarbonate. Composition (A) was kneaded in an extruder set to 250° C.,extruded to mirror-surface cast rolls through a T-die connected to anextruder set to 230° C. following extrusion, and while cooling the backsurface with a cooling device, herringbone-embossed with an embossingroll 0.5 mm deep that had been heated to 100° C., to obtain anunstretched film. The film was heated to 160° C. and stretched 4.6-foldin the longitudinal direction with a longitudinal stretching devicecomprising a group of rolls of varying peripheral speeds.

[0108] Compositions (B) and (C) that were identical in blendingcomposition to Composition (A) were melted and kneaded in an extruderset to 240° C. and extrusion laminated onto the both sides of thestretched film of Composition (A) that had been obtained as set forthabove, to obtain a three-layer laminate (B/A/C).

[0109] The three-layer laminate obtained was heated to 160° C. in atenter oven and stretched 9-fold in the traverse direction. It was thenpassed through a heat set zone (set to a temperature of 165° C.)connected to the tenter oven.

[0110] The both surfaces of the film were treated by corona discharge atan applied energy density of 90 W·min/m². A roll coater was then used toapply to the both surfaces an aqueous solution containing anequal-quantity mixture of butyl-modified polyethyleneimine, anethyleneimine adduct of polyaminepolyamide, and an acrylic acidalkylester copolymer having a quaternary ammonium salt structure in acoating amount of about 0.1 g/m² per side after drying and the coatingwas dried. The thicknesses of the layers constituting the three-layerlaminate film obtained (B/A/C) was 25/50/25 micrometers.

[0111] The forgery-preventing film obtained had a regular pattern ofwhite stripes derived from embossing between layers (A) and (B) andbetween layers (A) and (C).

Example 2

[0112] Composition (A), identical to that in Example 1, was kneaded inan extruder set to 250° C. and extruded to mirror-surface cast rollsthrough a T-die connected to an extruder set to 230° C., and the backsurface thereof was cooled by a cooling device to obtain an unstretchedfilm. The film was heated to a temperature of 160° C., sprayed withwater by a device positioned in proximity to the roll for longitudinalstretching, and longitudinally stretched 4.2-fold by rolls of differingperipheral speeds. Operations identical to those in Example 1 were thenconducted to obtain a three-layer laminate film of 90 micrometers thick.The thickness of the layers constituting the three-layer laminate filmobtained (B/A/C) was 20/50/20 micrometers. The forgery-preventing filmobtained had irregular pattern of white stripes between layers (A) and(B) and between layers (A) and (C).

Example 3

[0113] Composition (A) identical to that in Example 1,ethylene-propylene copolymer (b) with an MFR of 4 g/10 min and a meltingpoint of 137° C. (DSC peak temperature), and metallocene polyethylene(c) with an MFR of 4 g/10 min, a density of 0.91 g/cm³ and a meltingpoint of 110° C. (DSC peak temperature) were coextruded through a T-dieconnected to an extruder set to 230° C. to obtain a (b)/(A)/(c)three-layer laminate. The laminate was heated to 155° C., longitudinallystretched 4.6-fold with a longitudinal stretching device comprised of agroup of rolls of differing peripheral speeds, and wound onto a roll. Auniaxially stretched film (D) with a thickness of 50 micrometers and anopacity of 20 percent was thus obtained. An image reduced to {fraction(1/9)}^(th) original size in a direction perpendicular to the stretchingdirection was printed with an on-site color printer CB-418-T1 made byTEC on the (b) side of rolled film (D).

[0114] Separately, Composition (A) identical to that in Example 1 waskneaded in an extractor set to 250° C., extruded to mirror-surface castrolls through a T-die connected to an extruder set to 230° C., and theback surface was cooled with a cooling device to obtain an un stretchedfilm. The film was heated to 155° C. and longitudinally stretched4.6-fold with a longitudinal stretching device comprised of a group ofrolls of differing peripheral speeds to obtain a longitudinallystretched film of Composition (A).

[0115] The longitudinally stretched film of Composition (A) was stackedon, and in contact with, the (c) side of uniaxially stretched film (D)obtained as set forth above (uniaxially stretched film (D) was fed fromthe roll) to obtain a two-layer laminate (D/A). Compositions (B) and (C)of the same composition as in Example 1 were extruded with an extruderset to 240° C. onto either side of laminate (D/A) to obtain a four-layerlaminate (B/D/A/C).

[0116] The four-layer laminate thus obtained was heated in a tenter ovento 160° C. and stretched 9-fold in the traverse direction. It was thenpassed through a heat set zone (set to a temperature of 165° C.)connected to the tenter oven to obtain a four-layer laminate film of 110micrometers thick. The thickness of the layers constituting thefour-layer laminate film (B/D/A/C) was 25/5/55/25 micrometers. The filmobtained had a forgery-preventing layer (D) between layers (A) and (B).

Test Example 1

[0117] The porosity, opacity, and whiteness of each of theforgery-preventing films obtained in Examples 1-3 were measured. Theporosity was calculated from Equation (1) below:

Porosity (%)=((ρ₀−ρ)/ρ₀)×100  (Equ. 1)

[0118] ρ₀ in Equation 1 denotes the true density of the stretched filmand ρ denotes the density (JIS P-8118) of the stretched film. So long asthe material did not contain a large amount of air prior to stretching,the true density was nearly equal to the density before stretching.

[0119] Further, patterns were printed on both sides of each of theforgery-preventing films with offset printing inks POP·K black, POP·Kindigo blue, POP·K red, and POP·K yellow made by Dainippon Ink KagakuKogyo (K.K.). Unprinted portions in the form of 20 mm circles were leftso that watermarks remained.

[0120] The above-described printed forgery-preventing films wereemployed as originals and color copies were made with a color copier(Docu Color 1250, made by Fuji Xerox Co.). Pulp paper and OHP filmcomprised of biaxially-stretched polyethylene terephthalate wereemployed as the copy medium. An evaluation was conducted to determinewhether the pattern of white stripes of the watermarks was copied basedon the following scale.

[0121] [Evaluation Scale for Films of Examples 1 and 2]

[0122] O: The irregular pattern of white stripes of watermarks was notcopied. The watermarks remained white when pulp paper was employed asthe copy medium, and the watermarks became transparent when OHP film wasemployed.

[0123] X: The irregular pattern of white stripes of the watermarks wascopied.

[0124] [Evaluation Scale for Film of Example 3]

[0125] O: The internal printed areas of the watermarks became unclear,differing from the original.

[0126] X: The internal printed areas of the watermarks were sharp, andcould not be distinguished from the original.

[0127] Further, an attempt was made to use the above-describedforgery-preventing film as a copy medium and make a copy of the originalwith a color copier. As a result, the heat of the transfer roll made itdifficult for the forgery-preventing film to pass (feeding wasimpossible), precluding color copies.

[0128] The results are given in Table 1: TABLE 1 Thick- Copy medium nessforgery- (micro- Porosity Opacity Whiteness Pulp preventing meters) (%)(%) (%) paper OHP film Example 1 100 2 21 90 O O not feedable Example 2 90 4 30 91 O O not feedable Example 3 110 5 35 93 O O not feedable

[0129] As will be understood from Table 1, when the forgery-preventingfilm of the present invention is copied, changes in the contrast andbrightness of the identification pattern permit the ready distinction ofthe forgery from the true item. The forgery-preventing film of thepresent invention tends not to develop wrinkles and is well suited toprinting and watermarks. Thus, it can be suitably employed in papermoney, securities, confidential documents, and the like.

Example 4

[0130] Forgery-preventing films were obtained by the same method as inExample 1 with the exception that a composition was prepared by blending60 weight parts of propylene homopolymer with an MFR of 4 g/10 min, 40weight parts of heavy calcium carbonate with an average particle size of3 micrometers, 3 weight parts of high-density polyethylene with an MFRof 10 g/10 min, and 0.7 weight parts of titanium dioxide with an averageparticle diameter of 0.2 micrometer, 0.05 weight part of3-methyl-2,6-di-t-butylphenol per a total of 100 weight parts ofpropylene homopolymer and heavy calcium carbonate, 0.08 weight part ofphenolic stabilizer (product name Irganox 1010, made by Ciba-Geigy Co.)per a total of 100 weight parts of propylene homopolymer and heavycalcium carbonate, and 0.05 weight part of phosphorus-based stabilizer(product name Weston 618, made by G. E. Plastics) per a total of 100weight parts of propylene homopolymer and heavy calcium carbonate, andthe obtained composition was employed as Compositions (B) and (C).

[0131] The forgery-preventing films obtained had white stripes inregular patterns derived from embossing between layers (A) and (B), andbetween layers (A) and (C).

Example 5

[0132] With the exception that the composition described in Example 4was employed as Compositions (B) and (C), forgery-preventing films wereobtained by the same method as in Example 2. The forgery-preventingfilms obtained had irregular pattern of white stripes between layers (A)and (B) and between layers (A) and (C).

Example 6

[0133] With the exception that the composition described in Example 4was employed as Compositions (B) and (C), forgery-preventing films wereobtained by the same method as in Example 3. The forgery-preventingfilms obtained had a printed forgery preventing layer (D) between layers(A) and (B).

Test Example 2

[0134] The opacity, whiteness, and porosity of each layer were measuredfor each of the forgery-preventing films of Examples 4-6. The porositywas obtained from a ratio of voids area determined by an image analyzer(Model Luzex IID, made by Nireko (K.K.)) that can analyze the voidsobserved in a photograph taken by electron microscopy. Each of theforgery-preventing films was evaluated under fluorescent light on thefollowing scale:

[0135] O: Forgery-preventing layer invisible in reflected light, visiblein transmitted light.

[0136] X: Forgery-preventing layer visible in both reflected andtransmitted light.

[0137] XX: Forgery-preventing layer invisible in both reflected andtransmitted light.

[0138] The results are given in Table 2. TABLE 2 Thick- ness (micro-Opacity Whiteness Porosity (%) Evaluation meters) (%) (%) A B C resultExample 4 100 83 90 4 30 31 O Example 5  90 75 87 4 23 23 O Example 6110 87 93 7 37 37 O

[0139] In the forgery-preventing film of the present invention, theidentification pattern cannot be seen in reflected light. However, sincethe brightness or contrast of the identification pattern changes intransmitted light, a forgery and the real item are readilydistinguished. Further, the forgery-preventing film of the presentinvention tends not to develop wrinkles and is well suited to printingand watermarks. Thus, it can be suitably employed in paper money,securities, confidential documents, and the like.

Example 7

[0140] Composition (A) was prepared by blending 87 weight parts ofpropylene homopolymer with an MFR of 4 g/10 min, 3 weight parts of heavycalcium carbonate with an average particle diameter of 3 micrometers, 10weight parts of high-density polyethylene with an MFR of 10 g/10 min,0.05 weight part of 3-methyl-2,6-di-t-butylphenol per a total of 100weight parts of propylene homopolymer and heavy calcium carbonate, 0.08weight part of phenolic stabilizer (product name Irganox 1010, made byCiba-Geigy Co.) per a total of 100 weight parts of propylene homopolymerand heavy calcium carbonate, and 0.05 weight part of phosphorus-basedstabilizer (product name Weston 618, made by G. E. Plastics) per a totalof 100 weight parts of propylene homopolymer and heavy calciumcarbonate. Composition A was extruded and kneaded at 250° C., andextruded through a T-die connected to an extruder set to 230° C. toobtain an un stretched film. This film was heated to 155° C. andlongitudinally stretched 4.6-fold in a longitudinal stretching devicecomprised of a group of rolls of differing peripheral speeds to obtain astretched film.

[0141] In an extruder set to 240° C., 50 weight parts of propylenehomopolymer (B1) with a melt viscosity of 200 Pa·s and 50 weight partsof metallocene polyethylene (B2) with a melt viscosity of 100 Pa·s weremelted and kneaded. This Composition (B), which had a difference in meltviscosity of 100 Pa·s, was extruded onto both surfaces of the stretchedfilm of Composition (A), to obtain a three-layer laminate (B/A/B). Themelt viscosities of the thermoplastic resins were measured at 230° C. ata shear rate of 1220 S⁻¹ with a Capillograph 1C (9.55 mm cylinderdiameter, L/D=10) made by Toyo Seiki (K.K.).

[0142] The three-layer laminate obtained was heated to 160° C. in atenter oven and then stretched 9-fold in the traverse direction. It wasthen passed through a hot set zone (set to 165° C.) connected to thetenter over.

[0143] Both sides of the film were corona discharge treated at anapplied energy density of 90 W·min/m². A roll coater was then used toapply to the both surfaces an aqueous solution containing anequal-quantity mixture of butyl-modified polyethyleneimine, anethyleneimine adduct of polyaminepolyamide, and an acrylic acidalkylester copolymer having a quaternary ammonium salt structure to acoating amount of about 0.1 g/m² per side after drying and the coatingwas dried. The thicknesses of the layers constituting the three-layerlaminate film obtained (B/A/B) were 20/50/20 micrometers.

[0144] The forgery-preventing film obtained had a transparent streakpattern in the run direction for use in preventing forgery.

Example 8

[0145] In an extruder set to 240° C., 50 weight parts of propylenehomopolymer (B1) with a melt viscosity of 200 Pa·s under a shear rate of1220 S⁻¹ at 230° C. and 50 weight parts of 230° C. styrene graftpolyethylene (B2) with a melt viscosity of 100 Pa·s under a shear rateof 1220 S⁻¹ at 230° C. were melted and kneaded. This Composition (B),which had a difference in melt viscosity of 100 Pa·s, was extruded by anextruder and laminated onto both surfaces of a stretched film ofComposition (A) obtained in the same manner as in Example 7, to obtain athree-layer laminate (B/A/B). The same operations as in Example 7 werethen conducted to obtain a three-layer laminate film. The thicknesses ofthe layers (B/A/B) were 23/50/23 micrometers.

[0146] The forgery-preventing film obtained had a streak pattern in therun direction for use in preventing forgery.

Test Example 3

[0147] Porosity defined by Equation (1), opacity, and whiteness of theforgery-preventing films obtained in Examples 7 and 8 were measured.

[0148] Further, patterns were printed by the same method as in TestExample 1 on the various forgery-preventing films, and copying wasattempted onto pulp paper and OHP film. Evaluation was conductedaccording to the same scale as employed for the film of Examples 1 and2.

[0149] An attempt was also made to employ the above-described films forforgery prevention as a copy medium and make a copy of an original witha color copier. As a result, the heat of the transfer roll made itdifficult for the forgery-preventing film to pass (feeding wasimpossible), precluding color copies.

[0150] The results are given in Table 3: TABLE 3 Thick- Copy medium nessforgery- (micro- Porosity Opacity Whiteness Pulp preventing meters) (%)(%) (%) paper OHP film Example 7 90 4 25 90 O O not feeddable Example 896 5 45 91 O O not feeddable

[0151] As will be understood from Table 3, when the forgery-preventingfilm of the present invention is copied, change in the brightness of theidentification pattern permits the ready distinction of the forgery fromthe true item. The forgery-preventing film of the present inventiontends not to develop wrinkles and is well suited to printing andwatermarks. Thus, it can be suitably employed in paper money,securities, confidential documents, and the like.

Example 9

[0152] Composition (A) was prepared by blending 87 weight parts ofpropylene homopolymer with an MFR of 4 g/10 min, 3 weight parts of heavycalcium carbonate with an average particle diameter of 3 micrometers, 10weight parts of high-density polyethylene with an MFR of 10 g/10 min,0.05 weight part of 3-methyl-2,6-di-t-butylphenol per a total of 100weight parts of propylene homopolymer and heavy calcium carbonate, 0.08weight part of phenolic stabilizer (product name Irganox 1010, made byCiba-Geigy Co.) per a total of 100 weight parts of propylene homopolymerand heavy calcium carbonate and 0.05 weight part of phosphorus-basedstabilizer (product name Weston 618, made by G. E. Plastics) per a totalof 100 weight parts of propylene homopolymer and heavy calciumcarbonate.

[0153] Next, Composition (B) was prepared by blending 65 weight parts ofpropylene homopolymer with an MFR of 4 g/10 min, 30 weight parts ofheavy calcium carbonate with an average particle diameter of 10micrometers, 5 weight parts of high-density polyethylene with an MFR of10 g/10 min, 0.05 weight part of 3-methyl-2,6-di-t-butylphenol per atotal of 100 weight parts of propylene homopolymer and heavy calciumcarbonate, 0.08 weight part of phenolic stabilizer (product name Irganox1010, made by Ciba-Geigy Co.) per a total of 100 weight parts ofpropylene homopolymer and heavy calcium carbonate and 0.05 weight partof phosphorus-based stabilizer (product name Weston 618, made by G. E.Plastics) per a total of 100 weight parts of propylene homopolymer andheavy calcium carbonate.

[0154] Compositions (A) and (B) were extruded and kneaded at 250° C.,and extruded through a T-die connected to an extruder set to 230° C. toobtain a three-layer laminate (B/A/B). This film was heated to 155° C.and longitudinally stretched 4.6-fold in a longitudinal stretchingdevice comprised of a group of rolls of differing peripheral speeds toobtain a stretched film.

[0155] Additionally, Composition (D) of the same blend composition asComposition (A) was melted and kneaded in an extruder set to 240° C. andthen extrusion laminated onto both sides of the three-layer laminatestretched film obtained above to obtain a five-layer laminate(DIB/A/B/D).

[0156] The five-layer laminate was heated to 160° C. in a tenter oven,stretched 9-fold in the traverse direction, and then passed through aheat set oven (set to a temperature of 165° C.) connected to the tenteroven.

[0157] The two surfaces of the film were treated by corona discharge atan applied energy density of 90 W·min/m². A roll coater was then used toapply to the both surfaces an aqueous solution containing anequal-quantity mixture of butyl-modified polyethyleneimine, anethyleneimine adduct of polyaminepolyamide, and an acrylic acidalkylester copolymer having a quaternary ammonium salt structure to acoating amount of about 0.1 g/m² per side after drying and the coatingwas dried. The thicknesses of the layers constituting the five-layerlaminate film obtained (D/B/A/B/D) was 24/2/48/2/24 micrometers.

[0158] The forgery-preventing film obtained had an irregular pattern ofwhite stripes derived from voids in the (B) layers.

Example 10

[0159] In the same manner as in Example 9, Composition (A) was kneadedin an extruder set to 250° C. and extruded through a T-die connected toan extruder set to 230° C., and the back side was cooled with a coolingdevice to obtain an un stretched film. The film was heated to atemperature of 160° C. and longitudinally stretched 4.6-fold by rolls ofdiffering peripheral speeds.

[0160] Above-described Composition (A) and Compositions (D) and (B) ofthe same blend compositions as in Example 9 were coextruded from anextruder set to 240° C. to laminate the stretched film of Composition(A) obtained as set forth above, to obtain a five-layer laminate(B/D/A/D/B). The same operations were then conducted as in Example 9 toobtain a five-layer laminate film. The thickness of the layers(B/D/A/D/B) was 2/20/50/20/2 micrometers.

[0161] The film obtained had irregular pattern of white stripes derivedfrom voids in the B layers.

Test Example 4

[0162] The porosity, opacity, and whiteness of the variousforgery-preventing films obtained in Examples 9 and 10 were measured.The porosity was obtained from a ratio of voids area determined by animage analyzer (Model Luzex IID, made by Nireko (K.K.)) that can analyzethe voids observed in a photograph taken by electron microscopy.Further, a pattern was printed by the same method as in Text Example 1on each of the forgery-preventing films obtained and attempts were madeto make copies on pulp paper and OHP film. Evaluation was conducted onthe same scale as for the films of Examples 1 and 2.

[0163] Further, an attempt was made to use the above-describedforgery-preventing film as a copy medium and make a copy of the originalwith a color copier. As a result, the heat of the transfer roll made itdifficult for the forgery-preventing film to pass (feeding wasimpossible), precluding color copies.

[0164] The results are given in Table 4. TABLE 4 Copy medium Porosity(%) White- forgery- All Layer Layer Layer Opacity ness Pulp preventinglayers A B D (%) (%) paper OHP film Example 9 6 9 40 1 35 90 O O notfeedable Example 10 6 7 28 1 34 90 O O not feedable

[0165] As will be understood from Table 4, when the forgery-preventingfilm of the present invention is copied, change in the brightness of theidentification pattern permits the ready distinction of the forgery fromthe true item. The forgery-preventing film of the present inventiontends not to develop wrinkles and is well suited to printing andwatermarks. Thus, it can be suitably employed in paper money,securities, confidential documents, and the like.

Example 11

[0166] Composition (A) was prepared by blending 87 weight parts ofpropylene homopolymer with an MFR of 4 g/10 min, 3 weight parts of heavycalcium carbonate with an average particle diameter of 3 micrometers, 10weight parts of high-density polyethylene with an MFR of 10 g/10 min,0.05 weight part of 3-methyl-2,6-di-t-butylphenol per a total of 100weight parts of propylene homopolymer and heavy calcium carbonate, 0.08weight part of phenolic stabilizer (product name Irganox 1010, made byCiba-Geigy Co.) per a total of 100 weight parts of propylene homopolymerand heavy calcium carbonate and 0.05 weight part of phosphorus-basedstabilizer (product name Weston 618, made by G. E. Plastics) per a totalof 100 weight parts of propylene homopolymer and heavy calciumcarbonate. Composition (A) was kneaded in an extruder set to 250° C.,extruded to mirror-surface cast rolls through a T-die connected to anextruder set to 230° C., and the one side was cooled with a coolingdevice to obtain an un stretched film. The film was heated to 160° C.and longitudinally stretched 4.6-fold with a longitudinal stretchingmachine comprised of a group of rolls of differing peripheral speeds.

[0167] Next, a biaxially stretched polyester film of 12 micrometersthick (product name FE2000, made by Nimura Kagaku Kogyo (K.K.)) wascorona treated on both sides and an acrylic emulsion was coated thereonusing a bar coater in 1 g/m². The film was then gravure printed withcharacters in the size of 0.7 mm around using fluorescent pigment ink.The film was cut to a width of 1.0 mm with a microslitter, and thethermoplastic resin tape obtained was employed as a structural component(M) in the run direction of a polymer net.

[0168] Similarly, unstretched metallocene polyethylene film of 40micrometers thick and containing 200 ppm of the fluorescent whiteningagent East Brite OB-1 (made by Eastman Kodak) was cut to a width of 1.0mm with a microslitter and the thermoplastic resin tape obtained wasemployed as a structural component (T) in the traverse direction of thepolymer net.

[0169] The tapes were plain woven and heat fused with a hot press. Theobtained cloth (D) had a warp and woof of 12 mesh and an opening ratioof about 28 percent.

[0170] Cloth (D) was placed on, and in contact with, the surface of thelongitudinally stretched film of Composition (A) (Cloth (D) was fed froma roll on which it had been wound) to obtain a two-layer laminate (D/A).Compositions (B) and (C) identical in Composition to Composition (A)were melted and kneaded in an extruder set to 240° C. and extruded ontoeither side of this laminate (D/A) to obtain a four-layer laminate(B/D/A/C).

[0171] The four-layer laminate obtained was heated to 160° C. in atenter oven and then stretched 9-fold in the traverse direction. It wasthen passed through a heat set zone (set to a temperature of 165° C.)connected to the tenter oven.

[0172] The two surfaces of the film were treated by corona discharge atan applied energy density of 90 W·min/m². A roll coater was then used toapply to the both surfaces an aqueous solution containing anequal-quantity mixture of butyl-modified polyethyleneimine, anethyleneimine adduct of polyaminepolyamide, and an acrylic acidalkylester copolymer having a quaternary ammonium salt structure in acoating amount of about 0.1 g/m² per side after drying and the coatingwas dried. The thicknesses of the layers constituting the four-layerlaminate film obtained (B/D/A/C) were 10/15/50/25 micrometers.

[0173] The forgery-preventing film obtained had a regular grid patternderived from the polymer net between layers (A) and (B).

Example 12

[0174] Hot melt adhesive was applied with a bar coater to a thickness ofabout 10 micrometers to a polyimide film of 12.5 micrometers thick(product name: Apical 12.5H, made by Kanegafuchi Kagaku Kogyo (K.K.)).The film was then gravure printed with characters in the size of 0.7 mmaround using fluorescent pigment ink. The film was cut to a width of 1.0mm with a microslitter, and the thermoplastic resin tape obtained wasemployed as the structural component (M) in the run direction of apolymer net. The remainder of the process was conducted as in Example11. The thickness of the layer constituting the four-layer laminate filmobtained (B/D/A/C) of about 10/15/50/25 micrometers.

Example 13

[0175] Composition (A) was prepared by blending 75 weight parts ofpropylene homopolymer with an MFR of 4 g/10 min, 14.6 weight parts ofheavy calcium carbonate with an average particle diameter of 3micrometers, 0.4 weight parts of titanium dioxide with an averageparticle diameter of 0.21 micrometer, 10 weight parts of high-densitypolyethylene with an MFR of 10 g/10 min, 0.05 weight part of3-methyl-2,6-di-t-butylphenol per a total of 100 weight parts ofpropylene homopolymer and heavy calcium carbonate, 0.08 weight part ofphenolic stabilizer (product name Irganox 1010, made by Ciba-Geigy Co.)per a total of 100 weight parts of propylene homopolymer and heavycalcium carbonate and 0.05 weight part of phosphorus-based stabilizer(product name Weston 618, made by G. E. Plastics) per a total of 100weight parts of propylene homopolymer and heavy calcium carbonate.Composition (A) was kneaded in an extruder set to 250° C., extruded tomirror-surface cast rolls through a T-die connected to an extruder setto 230° C., and the one side was cooled with a cooling device to obtainan un stretched film. The film was heated to 160° C. and longitudinallystretched 4.6-fold with a longitudinal stretching machine comprised of agroup of rolls of differing peripheral speeds.

[0176] Next, a biaxially stretched polypropylene film of 25 micrometersthick (product name P2261, made by Toyo Hoseki (K.K.)) was coronatreated on both sides and an acrylic emulsion was applied with a barcoater in 1 g/m². The film was then gravure printed with characters inthe size of 0.7 mm around using fluorescent pigment ink. The film wascut to a width of 1.0 mm with a microslitter, and the thermoplasticresin tape obtained was employed as a structural component (M) in therun direction of a polymer net.

[0177] Similarly, unstretched polypropylene film of 40 micrometers thickthat contains 200 ppm of the fluorescent whitening agent East Brite OB-1(made by Eastman Kodak) was cut to a width of 1.0 mm with a microslitterand the thermoplastic resin tape obtained was employed as a structuralcomponent (T) in the traverse direction of the polymer net. Theremainder of the process was conducted as in Example 11. The four-layerlaminate film obtained had individual film thicknesses (B/D/A/C) ofabout 20/10/50/25 micrometers.

Test Example 5

[0178] The Equation (1) porosity, opacity, and JIS K7128 tear strengthof the various forgery-preventing films obtained in Examples 11-13 weremeasured. The following tests were also conducted.

[0179] (1) Copying Test on a Color Copier

[0180] Color copies were made using a color copier (Docu Color 1250,made by Fuji-Xerox) with the various forgery-preventing films as theoriginals. Pulp paper and OHP film comprised of biaxially-stretchedpolyethylene terephthalate film were employed as the copy media. Thegrid pattern of the polymer net and whether or not the printing on thepolymer net was copied were evaluated on the following scale.

[0181] Impossible: The grid pattern derived from the polymer net was notcopied and the printing applied to the polymer net was printed butunclear.

[0182] Possible: Both the grid pattern derived from the polymer net andthe printing on the polymer net were copied.

[0183] (2) Color Copier Paper Feeding Test

[0184] Copying was attempted with a color copier using the variousforgery-preventing films as copy media and the paper feed property wasevaluated on the following scale.

[0185] Impossible: Paper feeding was difficult due to heat from thetoner fixing rolls (there was fusion to the roll and distortion),precluding color copying.

[0186] Possible: There was no difficulty in feeding paper and colorcopying was possible.

(3) The Possibility of Recognition With UV Light

[0187] The appearance when exposed to ultraviolet lamp UVGL-58 (made byUltraviolet Co.) of each of the forgery-preventing films was evaluatedby naked eye based on the following scale.

[0188] O: Structural components in the traverse direction of the polymernet that were invisible under white light glowed bluish white and wererecognized.

[0189] X: No change was observed with UV exposure.

[0190] The results are given in Table 5. TABLE 5 Thick- ness TearRecognition (micro- Porosity strength Opacity Whiteness Copying by Paperfeeding under UV meters) (%) (gf) (%) (%) color copier in color copierradiation Example 11 100 4 45 30 90 Impossible Impossible O Example 12100 5 60 32 91 Impossible Impossible O Example 13 105 12  30 84 93Impossible Impossible O

[0191] Since the pattern derived from the polymer net and the brightnessand contrast of printed areas changed when the forgery-preventing filmof the present invention was copied, the copy and the real item werereadily distinguishable. Further, the forgery-preventing film of thepresent invention tends not to develop wrinkles, is suited to printing,and has substantial tear strength.

[0192] As described above, the forgery-preventing film of the presentinvention permits the ready distinction of copies from original items.Further, since the forgery-preventing film of the present inventiontends not to develop wrinkles, is well suited to printing, and hassubstantial tear strength, it can be advantageously employed on papermoney, securities, confidential documents, and the like.

[0193] The present disclosure relates to the subject matter contained inPCT Application PCT/JP01/08101 filed on Sep. 18, 2001, Japanese PatentApplication No. 281933/2000 filed on Sep. 18, 2000, Japanese PatentApplication No. 281934/2000 filed on Sep. 18, 2000, Japanese PatentApplication No. 281935/2000 filed on Sep. 18, 2000, Japanese PatentApplication No. 336161/2000 filed on Nov. 2, 2000 and Japanese PatentApplication No. 336162/2000 filed on Nov. 2, 2000. These applicationsare expressly incorporated herein by reference in its entirety.

[0194] The foregoing description of preferred embodiments of theinvention has been presented for purposes of illustration anddescription, and is not intended to be exhaustive or to limit theinvention to the precise form disclosed. The description was selected tobest explain the principles of the invention and their practicalapplication to enable others skilled in the art to best utilize theinvention in various embodiments and various modifications as are suitedto the particular use contemplated. It is intended that the scope of theinvention not be limited by the specification, but be defined claims setforth below.

What is claimed is:
 1. A forgery-preventing film having, on one side ofa first layer (A) comprising a thermoplastic resin, a second layer (B)comprising a thermoplastic resin wherein said film satisfying at leastone of Conditions 1 to 4 below: Condition 1: one side of said firstlayer (A) is treated to prevent forgery and said second layer (B) isformed on the surface of the treated side of said first layer (A);Condition 2: said second layer (B) comprises at least two thermoplasticresins of different melt viscosities; Condition 3: porosity of saidsecond layer (B) is greater than porosity of said first layer (A); andCondition 4: a polymer net is formed on one side of said first layer (A)and said second layer (B) is formed on the surface having the polymernet.
 2. The forgery-preventing film according to claim 1, wherein athird layer (C) is formed on the back side of said first layer (A). 3.The forgery-preventing film according to claim 1 wherein said firstlayer (A) is of a multilayer structure.
 4. The forgery-preventing filmaccording to claim 1 satisfying Condition
 1. 5. The forgery-preventingfilm according to claim 4 wherein both surfaces of said first layer (A)are treated to prevent forgery, and said second layer (B) and said thirdlayer (C) are formed on each of the treated surfaces of said first layer(A).
 6. The forgery-preventing film according to claim 4 wherein saidforgery-preventing treatment is embossing.
 7. The forgery-preventingfilm according to claim 4 wherein said forgery-preventing treatment isprinting.
 8. The forgery-preventing film according to claim 4 whereinthe opacity is from 1 to 60 percent.
 9. The forgery-preventing filmaccording to claim 4 wherein the porosity of said first layer (A) isfrom 0 to 40 percent and the porosity of said second layer (B) isgreater than 20 percent and less than or equal to 40 percent.
 10. Theforgery-preventing film according to claim 9 wherein a third layer (C)with a porosity of greater than 20 percent and less than or equal to 40percent is formed on the back side of said first layer (A).
 11. Theforgery-preventing film according to claim 9 which has an opacity ofgreater than 60 percent and less than or equal to 99 percent.
 12. Theforgery-preventing film according to claim 1 satisfying Condition
 2. 13.The forgery-preventing film according to claim 12 wherein the differencein the melt viscosity of said two thermoplastic resins of differing meltviscosity contained in said second layer (B) is greater than 50 Pa·s.14. The forgery-preventing film according to claim 12 wherein a thirdlayer (C) comprising at least two thermoplastic resins of different meltviscosities is formed on the back side of said first layer (A).
 15. Theforgery-preventing film according to claim 14 wherein the difference inmelt viscosity of said two thermoplastic resins of differing meltviscosity contained in said third layer (C) is greater than 50 Pa·s. 16.The forgery-preventing film according to claim 12 which has an opacityof from 1 to 60 percent.
 17. The forgery-preventing film according toclaim 1 satisfying Condition
 3. 18. The forgery-preventing filmaccording to claim 17 wherein the ratio (A/B) of the porosity of saidfirst layer (A) to that of said second layer (B) is less than or equalto ⅓.
 19. The forgery-preventing film according to claim 17 wherein bothsaid first layer (A) and said second layer (B) comprise an inorganicfinepowder and/or an organic filler, and the average particle diameterof the inorganic finepowder and/or the organic filler contained in saidsecond layer (B) is larger than the average particle diameter of theinorganic finepowder and/or the organic filler contained in said firstlayer (A).
 20. The forgery-preventing film according to claim 17 whereina third layer (C) comprising a thermoplastic resin is formed on the backside of said first layer (A) and the porosity of said third layer (C) isgreater than that of said first layer (A).
 21. The forgery-preventingfilm according to claim 20 wherein the ratio (A/C) of the porosity ofsaid first layer (A) to that of said third layer (C) is less than orequal to ⅓.
 22. The forgery-preventing film according to claim 20wherein both said first layer (A) and said third layer (C) comprise aninorganic finepowder and/or an organic filler, and the average particlediameter of the inorganic finepowder and/or the organic filler containedin said third layer (C) is larger than the average particle diameter ofthe inorganic finepowder and/or the organic filler contained in saidfirst layer (A).
 23. The forgery-preventing film according to claim 17which has an opacity of from 10 to 60 percent.
 24. Theforgery-preventing film according to claim 1 satisfying Condition
 4. 25.The forgery-preventing film according to claim 24 wherein said polymernet is treated to prevent forgery.
 26. The forgery-preventing filmaccording to claim 24 wherein said film is stretched in at least onedirection.
 27. The forgery-preventing film according to claim 24 whereinsaid polymer net is comprised of a thermoplastic resin tape and has anetwork structure in the form of a grid.
 28. The forgery-preventing filmaccording to claim 27 wherein a constituent member (T) in the traversedirection of said polymer net is unstretched thermoplastic resin tape.29. The forgery-preventing film according to claim 24 which has anaverage traverse and longitudinal tear strength as described in JISK7128 is greater than or equal to 20 gf.
 30. The forgery-preventing filmaccording to claim 24 wherein a third layer (C) is formed on the backside of said first layer (A).
 31. The forgery-preventing film accordingto claim 24 wherein both sides of said first layer (A) are treated toprevent forgery, and a second layer (B) and a third layer (C) are formedon each of the treated surfaces of said first layer (A).
 32. Theforgery-preventing film according to claim 24 wherein said second layer(B) and said third layer (C) have an opacity of from 1 to 99 percent.